In this paper, a new algorithm based on processing differential current harmonics is proposed for digital differential protection of power transformers. This algorithm has been developed by considering different behaviors of second harmonic components of the differential currents under fault and inrush current conditions. In the new method, a criterion function is defined in terms of the time v...

An electronic current transformer with a B-dot sensor is proposed in this study. The B-dot sensor can realize the current measurement of the transmission line in a non-contact way in accordance with the principle of magnetic field coupling. The multiple electrodes series-opposing structure is applied together with differential input structures and active integrating circuits, which can allow th...

Power system protective relaying systems are striving to meet the demands of systems which are ever increasing in complexity. . High-speed digital relays must make decisions while the power system is still in transition. Understanding the operation and performance of microprocessor based relays requires new engineering tools. Current transformer (CT) and relay modeling are practical tools to ev...

power system overvoltages due to switching, lightning and other disturbances are the main problem for designers of the power transformers. once some frequencies of the incoming surges match with some of the natural frequencies of transformer winding, the resonance phenomenon is expected in transformer winding. the resonant overvoltages may destroy the insulation between turns and cause to insul...

The Jiles-Atherton (J-A) based current transformer (CT) core model provides accurate modelling of hysteresis and saturation effects and can effectively represent the remanence flux in CT cores. The disadvantage of the J-A CT is the relevant parameters are not easy to obtain. This paper develops a methodology to estimate the parameters for a J-A CT model from a B-H loop. The B-H loop is relative...

Transformer insulating oil nanofluid is made to improve dielectric and thermal properties of the oil by employing nanoparticles with proper properties. In the current work, nanofluids based on transformer mineral oil were prepared by three procedures using diamond nanoparticles with high thermal conductivity, as well as high dielectric properties. It was tried to consider the impacts of surfact...

With the increase in capacitor voltage transformer (CVT) operation life, CVT impedance changes, and short-time switching of overhead lines, it is very easy to cause a transient oscillation accident which participates, reduce insulation level CVT, even induce regional power grid easily breakdown, after long-term with defects. In this paper, whole network, including generator, grid, consumer, mod...

The delta primary transposed zigzag secondary (DTz) transformer has been designed and used to reduce the bad impacts of the harmonic in the distribution power system. The DTz transformer is constructed with delta connection in primary winding and the three transposed windings at the different core legs of secondary winding. The harmonic reduction method of the DTz transformer applies two basic ...

The power supply analysis and design results of Sherman and Hamacher are extended to include approximate solutions to the nonlinear equations that define the rectifier turn-on angles. Additionally, peak rectifier current solely as a function of ripple factor, as well as the inverse relationship, i.e., ripple factor as a function of peak rectifier current, are also provided. Simplified exact equ...

Photovoltaic systems integrated to the grid have received considerable attention around the world. They can be connected to the electrical grid via galvanic isolation (transformer) or without it (transformerless). Despite making galvanic isolation, low frequency transformer increases size, cost and losses. On the other hand, transformerless PV systems increase the leakage current (common-mode c...